Breath testing system with breath temperature sensor

ABSTRACT

An improvement in alcohol breath testing system wherein a breath temperature sensor is included in the breath input unit and means responsive to the sensor for altering the performance of the system.

[lite tates Patet 1 Murphy Jan. 15, 1974 1 BREATH TESTING SYSTEM WITH BREATH TEMPERATURE SENSOR [56] References Cited [75] Inventor: John E. Murphy, Skokie, 111. UNITED STATES PATENTS 2,879,663 3/1959 Thomas 23/255 E X [73-] Asslgnee' gi Warner Cmrpommn Chicago 3,338,087 8/1967 Moberg et a1. 73/23 3,476,516 11/1969 Curry 23/254 R [22] Filed: July 24, 1972 Primary Examiner-Robert M. Reese [21] Appl 2747l2 AttmeyD0na1d W. Banner et a1.

Related [1.5. Application Data [63] Continuation of Ser. No, 154,381, June 18, 1971, [57] ABSTRACT abandoned An improvement in alcohol breath testing system wherein a breath temperature sensor is included in the [g2] Eff/git]: breath input unit and means responsive to the sensor I d 4 E for altering the performance of the system.

23/255 B; 73/23, 25 26, 27 9 Claims, 2 Drawing Figures Breath Temp. Sensor Ther r n istor to Evaluator l 2|2 I I F Galn Control I I (Resistance I I Feedback) 214 1 i 83 I Vent 7O 2|5 I 40 4 I K I f [\Q [105 I Controller Detector I /P armor l p Output I I07 p 1 r Apparatus an F 1 l S Reflegence 19110 ource .1.

CROSS REFERENCE TO RELATED APPLICATIONS BACKGROUND OF THE INVENTION Alcoholic intoxication represents a major public health and safety problem in most countries in the world and especially in the United States of America. In America the motor vehicle is the principal means of transportation and millions of Americans drive their cars on the public highways each day. According to the America] Medical Associations Committee on Medicolegal Problems publication, Alcohol and the Impared Driver, auto accident costs, in 1965 alone, exceeded 8 billion dollars. In human terms, 3% million injuries were sustained in that year and 49 thousand Americans were killed in auto accidents. Although the contribution of alcohol intoxication to this terrible toll cannot be precisely determined, there is general agreement that, despite stringent anti-drunk driving laws, alcohol intoxication is a factor in a majorportion of these accidents.

While various proposals and devices have been made in the past to deal with detection and control of the inebriate these have suffered from several drawbacks. Chemical testing devices tend to be inconvenient, difficult and sometimes dangerous for use by any but a welltrained technician. These devices also tend to be prohibitively expensive. Most of these devices allow for avoidance of an accurate test except in the case of direct and alert supervision. For example, breath tests to be accurate require a deep lung breath sample and can be evaded by inhaling and exhaling repetitively so as to test only oral or mixed breath. Other testers (such as that shown in U.S. Pat. No. 3,311,187), which involve agility, memory, eyesight and/or reaction-time testing do not test alcoholic intoxication as legally defined and allow for errors of inclusion and exclusion.

The term gas, as used herein and in the appended claims, embraces both ordinary air in the atmosphere, and breath exhaled from the lungsof a human subject.

Vehicle, as used herein and in the claims, means any human-guided self-propelled unit, such as an automobile, train, airplane, motorboat, on-and off-the road unit, such as snowmobile or bulldozer, and the like.

It has been discovered by experiments that human breath, including deep lung breath, varies in response factors such as previous activity, period in the environment, etc.

SUMMARY OF THE INVENTION The present invention takes advantage of these effects to improve the accuracy of the test system. A breath testing system in accordance with the present invention includes the improvement of a sensor for sensing the temperature of the breath supplied to the system and means, for altering the performance of the system in response to the sensed temperature.

Additional features of the present invention which are believed to be novel are detailed in the following description and are set forth with particularity in the appended claims. The invention, together with further advantages and features thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings, in the several figures of which like reference numerals identify like elements.

BRIEF oesciiiifirorvs 0% DRAIIVING DETAILED DESCRIPTION In accordance with the practice approved by the Commissioner of Patents in 34 Federal Register 833, the drawings and detailed description of the aforementioned application Ser. No. 136,921 is hereby incorporated by reference as if fully set out here.

The improvement in that system that is the subject of the present invention is best illustrated by reference to FIG. 1, hereof, wherein the improved system is generally designated llO. The System10 includes an input unit 211, which receives the exhaled breath and transfers it to a controller 40 from which it is coupled to a detector which is part of an evaluator 85. The detector produces an electrical output which is coupled to an amplifier 101 whose output is compared in a comparator with a reference signal from the source 107. The output of the comparator 105 serves as the *pass" or fail signal 87 and is coupled to the output apparatus 90.

As thus far described, the system 10 is identical to that of the aforementioned andincorporated by referenced application. In accordance with the present invention, the input apparatus 21 is provided with means for sensing the breath temperature which means may be a thermistor 210 mounted in the breath passageway 24F downstream of the opening 30 and upstream of the heater wire 64. The thermistor 210 is connected by electrical conductors 212, 214, to,form part of a gain control circuit 215 which serves as means responsive to the breath temperature sensing means, for controlling the overall response of the system 10'.

The circuit 215 is a resistive feedback circuit from the output 103 of the amplifier 101 to its input, as is best shown in FIG. 2 hereof. Referring to FIG. 2 the circuit of the detector 70 is shown in greater detail and, includes a Wheatstone bridge circuit connected between a regulated source of d.c. potential (13+) and a reference or ground potential which bridge circuit in cludes a catalytically active element 70 and passive element 78 which are exposed to the breath sample as explained in detail in the incorporated material. The output of the bridge is taken from between the arm of the potentiometer 94 and the line 81' and is fed through, respectively, resistors 101A and 1018 to the primary negative and positive inputs of the operational amplifier 101. The feedback circuit 215 includes the thermistor 210 connected in series with a resistor 215A from the output 103 of the operational amplifier 101 to its primary negative input.

in overall operation the thermistor senses variations in breath temperature and in response thereto, changes its resistance. This change in resistance alters the feedback to the amplifier input to change its gain from a nominal level corresponding to a normal breath temperature to a higher gain for lower breath temperatures as to a lower gain for higher breath temperatures.

Of course the thermistor'may be used to alter the reference signal level or the comparator operation to achieve the same result.

While one particular embodiment of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed as the invention is:

1. In a breath testing system of the type in which a detector output electrical signal is derived from a detector which signal may reflect both breath alcohol content and breath temperature variation from a norm and which signal is thereafter processed to produce an output signal, the improvement comprising:

means for sensing the breath temperature of incoming breath; and

means for altering the production and processing of the detector output signal in deriving the output signal so that the effect of breath temperature variation from the norm is lessened.

2. The invention of claim 1, wherein:

said temperature sensing means is a temperature responsive device mounted in a breath input unit so as to be substantially in the breath flow path.

3. The invention of claim 2 wherein:

said temperature sensing means is a thermistor.

4. In a vehicle, having a breath testing system of the type having a breath input unit receiving a gas sample and adapted to have a driver exhale his breath in a continuous flow thereinto, and of the type having means for producing an electrical signal from the gas sample, and means for processing said signal which processing means includes an amplifier for amplifying that signal and a comparator for comparing the amplified signal to a reference signal and for producing an output signal indicative of a pass or fail condition, the improvement comprising:

a breath temperature sensor in the breath input unit for sensing the temperature of the gas sample received therein, said sensor being actively coupled to said processing means for altering the processing of the electric signal to compensate the processing for sensed temperature variations of the gas sample from a nominal temperature.

5. The invention of claim 4 wherein:

said breath temperature sensor is a thermistor; and l the amplifier of the signal processing means includes a feedback network which includes said thermistor;

whereby an automatic gain control is provided to compensate for variations in gas sample temperature.

6. The invention of claim 4 wherein said temperature sensor is a thermistor.

7. In a breath testing system of the type having a breath input unit, the improvement of:

a breath temperature sensor, and

means responsive to said sensor for altering the performance of the system.

8. In a breath tester of the type having a breath input unit:

a thermistor coupled to the breath input unit and responsive to the temperature of gas passing into said unit, and

means, including said thermistor, for developing a signal indicative of the temperature of the gas passing into said unit.

9. in a vehicle, having a breath testing system of the type having a breath input unit receiving a gas sample and adapted to have a driver exhale his breath thereinto, and of the type having means for producing an electric signal from the gas sample, and means for processing said signal, the improvement comprising:

a breath temperature sensor in the breath input unit for sensing the temperature of the gas sample re ceived therein, said sensor being actively coupled to said processing means for altering the processing of the electric signal. 

2. The invention of claim 1, wherein: said temperature sensing means is a temperature responsive device mounted in a breath input unit so as to be substantially in the breath flow path.
 3. The invention of claim 2 wherein: said temperature sensing means is a thermistor.
 4. In a vehicle, having a breath testing system of the type having a breath input unit receiving a gas sample and adapted to have a driver exhale his breath in a continuous flow thereinto, and of the type having means for producing an electrical signal from the gas sample, and means for processing said signal which processing means includes an amplifier for amplifying that signal and a comparator for comparing the amplified signal to a reference signal and for producing an output signal indicative of a ''''pass'''' or ''''fail'''' condition, the improvement comprising: a breath temperature sensor in the breath input unit for sensing the temperature of the gas sample received therein, said sensor being actively coupled to said processing means for altering the processing of the electric signal to compensate the processing for sensed temperature variations of the gas sample from a nominal temperature.
 5. The invention of claim 4 wherein: said breath temperature sensor is a thermistor; and the amplifier of the signal processing means includes a feedback network which includes said thermistor; whereby an automatic gain control is provided to compensate for variations in gas sample temperature.
 6. The invention of claim 4 wherein said temperature sensor is a thermistor.
 7. In a breath testing system of the type having a breath input unit, the improvement of: a breath temperature sensor, and means responsive to said sensor for altering the performance of the system.
 8. In a breath tester of the type having a breath input unit: a thermistor coupled to the breath input unit and responsive to the temperature of gas passing into said unit, and means, including said thermistor, for developing a signal indicative of the temperature of the gas passing into said unit.
 9. In a vehicle, having a breath testing system of the type having a breath input unit receiving a gas sample and adapted to have a driver exhale his breath thereinto, and of the type having means for producing an electric signal from the gas sample, and means for processing said signal, the improvement comprising: a breath temperature sensor in the breath input unit for sensing the temperature of the gas sample received therein, said sensor being actively coupled to said processing means for altering the processing of the elEctric signal. 